Ga doping disrupts C-C coupling and promotes methane electroproduction on CuAl catalysts

Abstract

The electrochemical CO 2 reduction reaction (CO 2 RR) provides a route to store intermittent electricity in the form of fuels like methane. We reasoned that disrupting C-C coupling while maintaining high ∗CO coverage could enhance methane selectivity and suppress the hydrogen evolution reaction (HER). We studied the effect of doping CuAl, a material at the top of the CO 2 RR activity and selectivity volcano plot, with elements having low ∗CO binding energies: Au, Zn, and Ga. Encouraged by initial improvements in selectivity to methane, we optimized the Ga content and showed that the presence of uniformly dispersed Ga is crucial in CO 2 RR-to-methane performance enhancement. We rule out porosity and roughness and conclude that the presence of Ga in the doped catalysts enables high methane selectivity. The Ga-doped CuAl catalysts achieve a methane Faradaic efficiency (FE) of 53% by suppressing HER to 23% in neutral electrolyte at −1.4 V versus reversible hydrogen electrode. • Tuning the CO 2 reduction reaction product distribution by disrupting C-C coupling • Porous Ga-doped CuAl catalysts were synthesized • Methane current density of 234 mA/cm 2 and faradaic efficiency of 53% were achieved • Stable operation over 10 h The energy grid needs to shift from fossil fuels to renewable energies, such as wind, solar, nuclear, and hydroelectric energy, in order for society to keep below the 1.5°C global warming threshold. One challenge in achieving this goal is the intermittency of wind and solar electricity. An approach is the electrically powered production of methane, a commodity for which the infrastructure for storage, transportation, and use is well developed. CO 2 RR-to-methane catalysts are in need of improved selectivity, productivity, and stability. Herein, we show how the CO 2 RR product distribution can be redirected from C 2+ products to methane by disrupting carbon-carbon coupling. The material design principles herein contribute to the roadmap for CO 2 RR electrocatalyst design. We shift the CO 2 reduction reaction (CO 2 RR) product distribution from C 2+ products toward methane. Ga doping in CuAl catalysts disrupts carbon-carbon coupling and results in a selectivity shift from ethylene to methane while maintaining low hydrogen evolution activity.